What defines a contract that lacks commitment from one or more parties involved?

The definition of a contract that lacks commitment from one or more parties is indeed best captured by the term "illusory." An illusory contract is characterized by the presence of vague or ambiguous terms that do not bind one or more parties to fulfill their obligations. This means that if a party can choose whether or not to perform their side of the agreement without incurring any legal obligation, the commitment is considered illusory.

In contrast, a valid contract is one that is legally binding and enforceable; it must contain clear terms and intentions from all involved parties. A voidable contract, on the other hand, is valid and enforceable until one party chooses to void it, usually based on certain conditions like misrepresentation or undue influence. An enforceable contract is one that can be upheld in a court of law, provided all legality requirements are met. Therefore, an illusory contract stands out as the correct descriptor for agreements where commitments are not sufficiently binding.